Quality assessment of compressed images: A comparison between two methods

With limited additional effort, one can obtain valuable information on the subjective performance of image compression schemes. The choice of an appropriate experimental technique, however, is not always trivial. We show that the different nature of the artifacts introduced by different coders causes problems when evaluations are carried out using direct numerical category scaling. We demonstrate this by comparing the results of a direct scaling method and a scaling technique in which subjects have to determine quality differences between all possible combinations of coded images.